The objective of the proposed research is to develop a laboratory-based diagnostic system for syphilis to be used on either oral fluid samples or serum/plasma. This system will employ an oral fluid collection device based on the existing FDA approved OraSure HIV-1 Oral Specimen Collection Device which collects an oral sample rich in oral mucosal transudate (OMT). Two enzyme-linked immunosorbent assays will be developed that are compatible with this device to detect both nontreponemal and treponemal antibodies. The nontreponemal assay will measure both IgG and IgM antilipoidal antibodies formed in response to lipoidal material released from damaged host cells early in infection as well as to lipid from the treponeme itself. The antigens used in this assay are biologically nonspecific and are modifications of the Venereal Disease Research Laboratory (VDRL) antigen that contains cardiolipin, cholesterol, and lecithin. The treponemal antibody test will be based on recombinant protein antigens, 17 kDa and TmpA (45 kDa) proteins, derived from the outer membrane of T. pallidum. This system will provide a powerful new tool to expand syphilis testing in the United States. Sample collection will be safe for health care workers and can be accomplished in settings where blood collection is not practical. PROPOSED COMMERCIAL APPLICATIONS: The incidence of syphilis is at an all time low in the US, yet testing levels remain high. In 1998, CDC launched a national syphilis elimination program. The additional funds provided to state and local health departments should expand testing levels. Testing based on a highly sensitive assay system using a noninvasive oral fluid sample will be a valuable tool for the syphilis elimination program.